gstreamer怎么用c语言抽帧

你可以使用GStreamer库来在C语言中抽取帧。下面是一个简单的示例代码，展示了如何使用GStreamer来抽取视频帧：

#include <gst/gst.h>

static gboolean bus_call(GstBus *bus, GstMessage *msg, gpointer data) {
    GMainLoop *loop = (GMainLoop *)data;

    switch (GST_MESSAGE_TYPE(msg)) {
        case GST_MESSAGE_EOS:
            g_print("End of stream\n");
            g_main_loop_quit(loop);
            break;
        case GST_MESSAGE_ERROR: {
            gchar *debug;
            GError *error;

            gst_message_parse_error(msg, &error, &debug);
            g_free(debug);

            g_printerr("Error: %s\n", error->message);
            g_error_free(error);

            g_main_loop_quit(loop);
            break;
        }
        default:
            break;
    }

    return TRUE;
}

int main(int argc, char *argv[]) {
    GMainLoop *loop;
    GstElement *pipeline, *source, *decoder, *sink;
    GstBus *bus;

    gst_init(&argc, &argv);
    loop = g_main_loop_new(NULL, FALSE);

    if (argc != 2) {
        g_printerr("Usage: %s <video file>\n", argv[0]);
        return -1;
    }

    pipeline = gst_pipeline_new("video-player");
    source = gst_element_factory_make("filesrc", "file-source");
    decoder = gst_element_factory_make("decodebin", "decoder");
    sink = gst_element_factory_make("autovideoconvert", "video-sink");

    if (!pipeline || !source || !decoder || !sink) {
        g_printerr("Not all elements could be created.\n");
        return -1;
    }

    g_object_set(G_OBJECT(source), "location", argv[1], NULL);

    gst_bin_add_many(GST_BIN(pipeline), source, decoder, sink, NULL);
    gst_element_link(source, decoder);
    gst_element_link(decoder, sink);

    g_signal_connect(decoder, "pad-added", G_CALLBACK(on_pad_added), sink);

    bus = gst_pipeline_get_bus(GST_PIPELINE(pipeline));
    gst_bus_add_watch(bus, bus_call, loop);
    gst_object_unref(bus);

    gst_element_set_state(pipeline, GST_STATE_PLAYING);
    g_main_loop_run(loop);

    gst_element_set_state(pipeline, GST_STATE_NULL);
    gst_object_unref(GST_OBJECT(pipeline));
    g_main_loop_unref(loop);

    return 0;
}

这个示例代码创建了一个GStreamer管道，并使用`filesrc`元素从指定的视频文件中读取数据。然后，使用`decodebin`元素解码视频流，并使用`autovideoconvert`元素进行格式转换。你可以根据需要修改和扩展这个代码，以满足你的具体需求。

请确保在编译时链接GStreamer库，并在运行代码之前设置正确的视频文件路径。